18381987 has 24 divisors (see below), whose sum is σ = 30102800. Its totient is φ = 10715328.

The previous prime is 18381973. The next prime is 18381989. The reversal of 18381987 is 78918381.

It is not a de Polignac number, because 18381987 - 2⁸ = 18381731 is a prime.

It is a Smith number, since the sum of its digits (45) coincides with the sum of the digits of its prime factors.

It is not an unprimeable number, because it can be changed into a prime (18381989) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1912 + ... + 6357.

Almost surely, 2^18381987 is an apocalyptic number.

18381987 is a deficient number, since it is larger than the sum of its proper divisors (11720813).

18381987 is a wasteful number, since it uses less digits than its factorization.

18381987 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8307 (or 8304 counting only the distinct ones).

The product of its digits is 96768, while the sum is 45.

The square root of 18381987 is about 4287.4219526424. The cubic root of 18381987 is about 263.9150467014.

The spelling of 18381987 in words is "eighteen million, three hundred eighty-one thousand, nine hundred eighty-seven".